1. FIELD OF THE INVENTION
The present invention relates to a kneecap or patella cutting device for the fitting of a total knee replacement or prosthesis.
The invention can be applied in an especially advantageous way in the field of bone resurfacing prosthesis relating to the knee joint.
Three-compartmental total knee replacements are constituted by a tibia part, a kneecap part and a femur part that has notably an artificial trochlea. In this type of prosthesis, the kneecap is designed to move in said artificial trochlea through said kneecap component.
2. DESCRIPTION OF THE PRIOR ART
Usually, in a total knee replacement operation, the anatomical kneecap is cut and then drilled through with locking holes for the implanting of the future kneecap component designed to cooperate with the artificial trochlea that is prepared in the femur component.
At present, kneecap cutting is always done separately from the femur and without any reference other than an anatomical one.
The result thereof is that, in certain cases, since the cutting is not parallel to the plane of the trochlea, the kneecap component is badly positioned. The kneecap is then unstable, and therefore often tends to get dislocated, i.e. to get out of the groove formed by the trochlea of the femur component. To put it briefly, the action of the kneecap during the bending and stretching of the knee may be likened to that of a pulley that compensates for the tendency of the femur/tibia joint to get dislocated. To the extent that the equivalent of the pulley is positioned crosswise, it tends to protrude and consequently to come out of the housing into which it is fitted.
For example, we may cite a cutting method in which the kneecap is firstly put out of joint and then held by forceps wherein it is cut or milled. However, this type of technique cannot be used to obtain a cutting of the kneecap that is perfectly parallel to the plane of trochlea of the femur component.
Hence, the technical problem to be resolved by the object of the present invention is that of proposing a kneecap cutting device, for the fitting of a total knee replacement, by which it is possible to obtain cutting that is systematically parallel to the plane of the trochlea.